Semiconductor power module and method of manufacturing the same

ABSTRACT

A semiconductor power module according to the present invention includes a base member, a semiconductor power device having a surface and a rear surface with the rear surface bonded to the base member, a metal block, having a surface and a rear surface with the rear surface bonded to the surface of the semiconductor power device, uprighted from the surface of the semiconductor power device in a direction separating from the base member and employed as a wiring member for the semiconductor power device, and an external terminal bonded to the surface of the metal block for supplying power to the semiconductor power device through the metal block.

This is a Continuation of U.S. application Ser. No. 13/247,105, filed onSep. 28, 2011, and allowed on May 14, 2013 as U.S. Pat. No. 8,525,315,the subject matter of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a semiconductor power module and amethod of manufacturing the same.

2. Description of Related Art

A semiconductor power module is an apparatus loaded with a plurality ofsemiconductor power devices for obtaining an output from thesemiconductor power devices electrically connected with one another.Such a semiconductor power module is employed for an inverter circuitconstituting a driver circuit for driving an electric motor, forexample. The electric motor is employed as a power source for anelectric car (including a hybrid car), an electric train or anindustrial robot, for example. The semiconductor power module is alsoapplied to an inverter circuit converting power generated by a powergenerator (particularly a private power generator) such as a solar cellor a wind power generator to match with the power of a commercial powersource.

The semiconductor power devices loaded on the semiconductor power moduleare connected to an external terminal of the semiconductor power modulethrough wires.

For example, a semiconductor power module disclosed in FIG. 1 of PatentDocument 1 (Japanese Unexamined Patent Publication No 2007-305962)includes a circuit board having a structure obtained by integrating ametal substrate electrode, an insulated substrate and a heat sink withone another, a plurality of SiC semiconductor power devices connected.onto the metal substrate electrode of the circuit board, a case fixed tothe heat sink for storing the SiC semiconductor power devices, and anexternal electrode mounted on the case. The SiC semiconductor powerdevices and the external electrode are connected with one anotherthrough Al wires.

SUMMARY OF THE INVENTION

The Al wires connected to the semiconductor power devices must feed highcurrent operated by the semiconductor power devices. In general,therefore, a plurality of Al wires are bonded to each semiconductorpower device.

Even if a plurality of Al wires are bonded to each semiconductor powerdevice, however, the bonding area between each Al wire and thesemiconductor power device is so small that current concentrates on thejunction between the Al wire and the semiconductor power device. Thewaveform of the current is disturbed due to the current concentration,to disadvantageously result in local heat generation in thesemiconductor power device. While the heat generated in thesemiconductor power device is partially released through the Al wire,the heat releasing effect is insufficient if the diameter of the Al wireis small.

When the number of the Al wires connected to each semiconductor powerdevice is increased thereby ensuring large bonding areas, a sufficientheat releasing effect may be attained. However, the pitch of the Alwires connected to the semiconductor power device is limited, and hencethe heat releasing effect is desirably improved by another technique.

Accordingly, a principal object of the present invention is to provide asemiconductor power module capable of leveling current flowing from asemiconductor power device and capable of efficiently releasing heatgenerated in the semiconductor power device and a method ofmanufacturing the same.

Another object of the present invention is to provide a method ofmanufacturing a semiconductor power module, capable of simplymanufacturing a semiconductor power module capable of leveling currentflowing from a semiconductor power device and capable of efficientlyreleasing heat generated in the semiconductor power device with highquality.

The foregoing and other objects, features and effects of the presentinvention will become more apparent from the following detaileddescription of the embodiments with reference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates the overall structure of a semiconductor power moduleaccording to a first embodiment of the present invention.

FIG. 2 illustrates the internal structure of the semiconductor powermodule shown in FIG. 1.

FIG. 3 is a sectional view of the semiconductor power module shown inFIG. 1, taken along a cutting plane line A-A in FIG. 1.

FIGS. 4A to 4E are sectional views, taken along the cutting plane lineA-A in FIG. 1 similarly to FIG. 3, successively showing partialmanufacturing steps for the semiconductor power module shown in FIG. 1.

FIG. 5 is a sectional view of the semiconductor power module shown inFIG. 1, taken along a cutting plane line A′-A′ in FIG. 1.

FIG. 6 illustrates the overall structure of a semiconductor power moduleaccording to a second embodiment of the present invention.

FIG. 7 illustrates the internal structure of the semiconductor powermodule shown in FIG. 7.

FIG. 8 is a sectional view of the semiconductor power module shown inFIG. 6, taken along a cutting plane line B-B in FIG. 6.

FIG. 9 is a sectional view of the semiconductor power module shown inFIG. 6, taken along a cutting plane line C-C in FIG. 6.

FIGS. 10A to 10E are sectional views, taken along the cutting plane lineB-B in FIG. 6 similarly to FIG. 8, successively showing partialmanufacturing steps for the semiconductor power module shown in FIG. 6.

FIG. 11 illustrates the internal structure of a semiconductor powermodule according to a modification of a metal block shown in FIG. 2.

FIG. 12 is a sectional view of the semiconductor power module accordingto the modification of the metal block shown in FIG. 3.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

A semiconductor power module according to an aspect of the presentinvention includes a base member, a semiconductor power device having asurface and a rear surface with the rear surface bonded to the basemember, a metal block, having a surface and a rear surface with the rearsurface bonded to the surface of the semiconductor power device,uprighted from the surface of the semiconductor power device in adirection separating from the base member and employed as a wiringmember for the semiconductor power device, and an external terminalbonded to the surface of the metal block for supplying power to thesemiconductor power device through the metal block.

According to this structure, the metal block having a larger diameterthan a wire is employed as the wiring member connecting thesemiconductor power device and the external terminal of thesemiconductor power module with each other. Thus, a wire can be bondedto the semiconductor power device with a large area. Therefore, thejunction between the wire (the metal block) and the semiconductor powerdevice can be prevented from current concentration. Consequently,current can be leveled. Further, heat generated in the semiconductorpower device can be efficiently released, whereby a heat releasingeffect can also be improved.

Preferably, the semiconductor power module according to the presentinvention further includes a case having a base portion provided with adevice region where the semiconductor power device is arranged and aframe portion fixed to the base portion for surrounding the deviceregion, and a top plate, made of resin, fixed to the frame portion ofthe case and opposed to the device region, while the external terminalincludes a plate terminal provided along the top plate, and the topplate has a support portion overlapping with the plate terminal in planview for supporting the plate terminal from the side of a rear surfacethereof.

When the external terminal is the plate terminal provided along the topplate blocking the case and the plate terminal is subjected to anexternal shock or the like, the shock may be transmitted to thesemiconductor power device through the metal block, to break thesemiconductor power device as a result.

According to this structure, therefore, the top plate has the supportportion supporting the plate terminal from the side of the rear surfacethereof. Even if the plate terminal is subjected to a shock or the like,therefore, the support portion can absorb the shock. Consequently, thesemiconductor power device can be absolutely protected againsttransmission of the shock, or the shock transmitted to the semiconductorpower device can be reduced. Therefore, the semiconductor power devicecan be prevented from breakage caused by the shock.

Preferably in the semiconductor power module according to the presentinvention, an opening smaller than the plane area of the plate terminalis formed in a region of the top plate opposed to the plate terminal,the metal block is bonded to the plate terminal through the opening, andthe support portion of the top plate includes a peripheral edge portionof the opening surrounding the metal block in the top plate.

According to this structure, the support portion constituted of theperipheral edge portion of the opening surrounding the metal block caneffectively absorb a shock transmitted from the plate terminal to themetal block.

Preferably in the semiconductor power module according to the presentinvention, the top plate is a member provided to be separable from theframe portion.

According to this structure, the top plate is separable from the frameportion. In order to manufacture the semiconductor power module,therefore, the semiconductor power device is first arranged on thedevice region so that the metal block can be bonded to the semiconductorpower device while e the top plate is separated from the frame portion.Therefore, the semiconductor power module can be manufactured withexcellent workability.

Preferably in the semiconductor power module according to the presentinvention, the top plate is formed in a U shape in plan view having anopen end on a position on one side with respect to the plate terminaland having a blocked end on a position on a side opposite to the openend with respect to the plate terminal, and supported by the frameportion to be slidable in a sliding direction along a direction wherethe blocked end separates from the plate terminal, the metal block isbonded to the plate terminal in a region surrounded by the top platebetween the open end and the blocked end, and the support portion of thetop plate includes an edge portion of the region in the top plate.

According to this structure, the top plate is slidably supported by theframe portion, and separable from the frame portion. In order tomanufacture the semiconductor power module, therefore, the semiconductorpower device is first arranged on the device region so that the metalblock can be bonded to the semiconductor power device while the topplate is separated from the frame portion. Therefore, the semiconductorpower module can be manufactured with excellent workability. Further, anend portion of the top plate opposite to the direction where the same isextracted by sliding forms the open end. Also after the top plate isfixed to the frame portion, therefore, the device region can be exposedby extracting the top plate without detaching the metal on from theplate terminal. Consequently, maintenance in the case can be easilyperformed.

Further, the support portion constituted of the edge portion surroundingthe region where the metal block is arranged can effectively absorb ashock transmitted from the plate terminal to the metal block.

Preferably in the semiconductor power module according to the presentinvention, the plate terminal is in the form of a quadrangle in planview having a pair of first opposite sides extending along the slidingdirection and a pair of second opposite sides orthogonal to the firstopposite sides, the top plate has a pair of arm portions along the firstopposite sides and a coupling portion coupling sides of the pair of armportions in the sliding direction with each other, and is provided tosurround three sides in the periphery of the plate terminal with the armportions and the coupling portion, the pair of arm portions have firstportions coming into contact with the peripheral edge portion of theplate terminal from outside in a transverse direction orthogonal to thesliding direction and second portions projecting from lower ends of thefirst portions along the rear surface of the plate terminalrespectively, and the peripheral edge portion of the plate terminalalong the first opposite sides fits into a recess portion partitioned bythe first portions of the arm portions and the second portions of thearm portions.

According to this structure, the peripheral edge portion of the plateterminal along the first opposite sides fits into the recess portionpartitioned by the first portions of the arm portions and the secondportions of the arm portions. When the top plate is slid along the frameportion, therefore, the plate terminal can he utilized as a guide memberfor guiding the top plate. Thus, the top plate can be easily positioned.

Preferably in the semiconductor power module according to the presentinvention, the coupling portion has a first portion coming into contactwith the peripheral edge portion of the plate terminal from outside inthe sliding direction and a second portion projecting from a lower endof the first portion along the rear surface of the plate terminal, andthe peripheral edge portion of the plate terminal along the secondopposite sides fits into a recess portion partitioned by the firstportion of the coupling portion and the second portion of the couplingportion.

According to this structure, the peripheral edge portion of the plateterminal along the second opposite sides (the opposite sides orthogonalto the sliding direction) fits into the recess portion partitioned bythe first portion of the coupling portion and the second portion of thecoupling portion. When the top plate is slid along the frame portion,therefore, the sliding of the top plate can be stopped by bringing theperipheral edge portion of the plate terminal into contact with thefirst portion of the coupling portion of the top plate. In other words,the plate terminal can also be utilized as a stopper member for stoppingthe sliding of the top plate. Therefore, the top plate can be moreeasily positioned.

Preferably in the semiconductor power module according to the presentinvention, both of the base portion and the frame portion are made of ametal, the base portion serves also as the base member supporting thesemiconductor power device, and the frame portion serves also as asecond external terminal for supplying power to the semiconductor powerdevice through the base portion.

According to this structure, the frame portion uprighted from the baseportion serves al so as the second external terminal, whereby electricalcontact with the rear surface of the semiconductor power device can beattained from the side of the surface of the semiconductor power module.

In the semiconductor power module according to the present invention,the semiconductor power device may be a device employing an SiCsemiconductor.

In this case, the metal block is preferably made of Cu or an alloymaterial containing Cu.

According to this structure, the difference between the linear expansioncoefficients of SiC and the wiring member can be reduced as comparedwith a case of employing an Al wire as the wiring member for thesemiconductor power device. Therefore, thermal stress caused between thesemiconductor power device and the wiring member can be reduced.Consequently, thermal fatigue of the semiconductor power device can bereduced, whereby a semiconductor power module having a long life andhigh reliability can be attained. The alloy material containing Cu canbe prepared from a CuMo alloy or a CuW alloy, for example.

For example, the linear expansion coefficient of SiC is about 4.5 ppm/K,and that of a CuMo alloy is about 9.0 ppm/K (about twice the linearexpansion coefficient of Sic). On the other hand, the linear expansioncoefficient of Al is about 23 ppm/K (about five times the linearexpansion coefficient of Sic).

The metal block may be in the form of a rectangular parallelepiped, ormay have a tapered shape whose sectional area spreads from the rearsurface toward the surface thereof.

If the metal block has a tapered shape, heat generated in thesemiconductor power device can be released with the optimum heatreleasing efficiency when designing the area of the rear surface of themetal block in response to the surface area of the semiconductor powerdevice and designing the area of the surface of the metal block inresponse to the size of the external terminal.

The semiconductor power module according to the present invention may beprovided with a plurality of semiconductor power devices, and theexternal terminal may be collectively bonded to the metal block bondedto each of the semiconductor power devices.

Preferably in the semiconductor power module according to the presentinvention, the top plate is provided with a through-hole passing throughthe top plate in the thickness direction in a region other than a regionoverlapping with the plate terminal in plan view.

According to this structure, an insulated state in the case can besimply maintained by pouring resin into the case from the through-holeformed in the top plate.

A method of manufacturing a semiconductor power module according toanother aspect of the present invention includes the steps of bonding arear surface of a semiconductor power device having a surface and therear surface to a base member, bonding a rear surface of a metal block,having a surface and the rear surface, employed as a wiring member forthe semiconductor power device to the surface of the semiconductor powerdevice after bonding the base member and the semiconductor power deviceto each other, performing preliminary soldering on an external terminal,for supplying power to the semiconductor power device, and bonding theexternal terminal and the metal block to each other by bringing themetal block into contact with a portion of the external terminalsubjected to the preliminary soldering and heating the externalterminal.

When the metal block having a high heat releasing effect is utilized asthe wiring material for the semiconductor power device as in the presentinvention, heat may be released through the metal block having a highheat releasing effect if the side of the external terminal is merelyheated while a solder material is held between the metal block and theexternal terminal. Consequently, the previously held solder material maynot be excellently melted, but the metal block and the external terminalmay be defectively bonded to each other.

According to the inventive manufacturing method, therefore, thepreliminary soldering is previously performed on the external terminal,and the metal block is brought into contact with and bonded to theportion subjected to the preliminary soldering. Thus, the metal blockand the external terminal can be excellently bonded to each other. Inother words, a semiconductor power device such as that according to thepresent invention can be simply manufactured with high quality.

Preferably in the method of manufacturing a semiconductor power moduleaccording to the present invention, the external terminal is a plateterminal in the form of a flat plate, and the step of performing thepreliminary soldering includes a step of piling not less than aprescribed volume of solder on the plate terminal.

According to this structure, the solder of not less than the prescribedvolume can compensate for a vertical difference caused between aplurality of metal blocks.

Embodiments of the present invention are now described in detail withreference to the attached drawings.

<First Embodiment>

FIG. 1 illustrates the overall structure of a semiconductor power moduleaccording to a first embodiment of the present invention.

A semiconductor power module 1 includes a case 2 having an open surface,a top plate 3 blocking the open surface of the case 2, a source terminal4 as an external terminal, a source sensing terminal 5, and a gateterminal 6.

For the convenience of illustration, directions X, Y and Z shown in FIG.1 may hereinafter be employed. The direction X is a direction along thelong sides of the case 2 rectangular in plan view. The direction Y is adirection along the short sides of the case 2 rectangular in plan view.The direction Z is a direction along the height direction of the case 2.When the case 2 is placed on a horizontal plane, the directions X and Yform two horizontal directions (first and second horizontal directions)along two horizontal straight lines (X- and Y-axes) orthogonal to eachother, and the direction Z forms a vertical direction (a heightdirection) along a vertical straight line (a Z-axis).

The case 2 integrally has a base portion 8, rectangular in plan view,having a uniform thickness and a frame portion 9, rectangular in planview, uprighted from a peripheral edge portion of the base portion 8. Inthe semiconductor power module 1, semiconductor power devices 18,described later, are arranged on a region (a device region 16 describedlater) of the base portion 8 surrounded by the frame portion 9.

The base portion 8 and the frame portion 9 are made of a metallicmaterial in the first embodiment. In particular, the base portion 8 andthe frame portion 9 are preferably made of a metal such as aluminum orcopper having high heat releasing characteristics.

A base 12 made of a resin material is mounted on the frame portion 9.The source sensing terminal 5 and the gate terminal 6 in the form ofnarrow columns are provided to extend inside and outside the case 2through the base 12. The source sensing terminal 5 and the gate terminal6 are so provided through the base 12 made of resin that the sourcesensing terminal 5 and the gate terminal 6 can be insulated from eachother and from the frame portion 9 made of a metal.

The top plate 3 is a platelike body, in the form of a rectangle having auniform thickness in plan view, separable from the case 2. The top plate3 is made of a resin material in the first embodiment. The top plate 3,particularly preferably made of heat-resistant resin such as PPS(polyphenylene sulfide), may alternatively be made of a liquid crystalpolymer or a ceramic material. The top plate 3 is fixed to the frameportion 9 with an adhesive or the like, for example.

The source terminal 4 is a platelike body (a plate terminal), in theform of a rectangle having a uniform thickness in plan view, elongatedalong the direction Y, and placed on the upper surface of the top plate3.

In the top plate 3, a plurality of openings 14 (shown by two-dot chainlines in FIG. 1) smaller than the plane area of the source terminal 4are formed in a region opposed to the source terminal 4. The pluralityof openings 14 are formed in the same number as the semiconductor powerdevices 18 described later. According to the first embodiment, threeopenings 14 are arrayed in a triangular shape in plan view.

In the top plate 3, a through-hole 15 passing through the top plate 3 inthe thickness direction is formed on a position between the sourceterminal 4 and the base 12. The through-hole 15 is in the form of anellipse elongated along the direction Y in plan view in the firstembodiment.

FIG. 2 illustrates the internal structure of the semiconductor powermodule 1 shown in FIG. 1. FIG. 3 is a sectional view of thesemiconductor power module 1 shown in FIG. 1, taken along a cuttingplane line A-A in FIG. 1.

In the case 2, an insulated substrate 17 and the plurality ofsemiconductor power devices 18 are arranged on the device region. 16surrounded by the frame port on 9 in this order from the side closer tothe base 12 along the direction Y.

The insulated substrate 17 is constituted of a ceramic substrate, forexample. The insulated substrate 17 is a platelike body, in the form ofa rectangle having a uniform thickness in plan view, elongated along thedirection Y, and a platelike source sensing wire 19 and a platelike gatewire 20 are formed thereon at an interval from each other. An end of thesource sensing terminal 5 is connected to the source sensing wire 19. Anend of the gate terminal 6 is connected to the gate wire 20.

The plurality of semiconductor power devices 18 include a plurality ofswitching elements Tr and a plurality of diode elements Di. According tothe first embodiment, the semiconductor power devices 18 include twoswitching elements Tr and one diode element Di. The semiconductor powerdevices 18 are devices employing an SiC semiconductor in the firstembodiment. The plurality of semiconductor power devices 18 are arrangedto be in one-to-one correspondence to the openings 14 of the top plate 3respectively. More specifically, one diode element Di and the twoswitching elements Tr are arrayed in a triangular shape in plan view.Rear surfaces 182 of the plurality of semiconductor power devices 18 arebonded to the base portion 8 of the case 2, so that the semiconductorpower devices 18 are electrically connected to the case 2.

Among the semiconductor power devices 18, the switching elements Tr areelectrically connected to the gate wire 20 and the source sensing wire19 through different Al wires 22 and 23 respectively.

Rear surfaces 242 of metal blocks 24 employed as wiring materialssupplying power to the semiconductor power devices 18 are bonded one byone to surfaces 181 (opposite to the rear surfaces 182 bonded to thebase portion 8) of the semiconductor power devices 18. The metal blocks24 are in the form of rectangular parallelepipeds uprighted from thesurfaces 181 of the semiconductor power devices 18 in a direction(approaching the source terminal 4) separating from the base portion 8in the first embodiment.

The metal blocks 24 are preferably made of Cu or an alloy material (suchas a CuMo alloy or a CuW alloy, for example) containing Cu. Thus, thedifference between the linear expansion coefficients of SiC and themetal blocks 24 can be reduced as compared with a case of employing Alwires as wiring members for the SiC power devices 18. Therefore, thermalstress caused between the semiconductor power devices 18 and the metalblocks 24 can be reduced. Consequently, thermal fatigue of thesemiconductor power devices 18 can be reduced, whereby a semiconductorpower module 1 having a long life and high reliability can be attained.For example, the linear expansion coefficient of SiC is about 4.5 ppm/K,and that of a CuMo alloy is about 9.0 ppm/K (about twice the linearexpansion coefficient of SiC). On the other hand, the linear expansioncoefficient of Al is about 23 ppm/K (about five time the linearexpansion coefficient of SiC). Surfaces 241 of the plurality of metalblocks 24 are bonded to the source terminal 4 through the openings 14 ofthe top plate 3.

In the top plate 3, a recess portion 25 having a contour along the shapeof the source terminal 4 in plan view (overlapping with the sourceterminal 4 in plan view) is formed on the region opposed to the sourceterminal 4, and the source terminal 4 is fitted into the recess portion25. The openings 14 for connecting the metal blocks 24 and the sourceterminal 4 with one another are formed to pass through a bottom. wall 26of the recess portion 25. A portion, surrounding the openings 14, of thebottom wall 26 of the recess portion 25 as a support portion is incontact with the source terminal 4 from the side of the rear surface.Thus, a part of the source terminal 4 is supported by the metal blocks24 due to the bonding, and most of the remaining parts are supported bythe top plate 3 (the bottom wall 26 of the recess portion 25) enteringthe side of the rear surface thereof.

FIGS. 4A to 4E are sectional views successively illustratingmanufacturing steps for the semiconductor power module 1 shown in FIG.1.

First, the insulated substrate 17 provided with the platelike wires 19and 20 is mounted on the device region 16 in the case 2, as shown inFIG. 4A. Then, the base 12 having the source sensing terminal 5 and thegate terminal 6 inserted thereinto is mounted on the frame portion 9 ofthe case 2. Then, the source sensing terminal 5 and the gate terminal 6and the platelike wires 19 and 20 are bonded to one another. Then, thesemiconductor power devices 18 are set on the base portion 8 throughplate solder members 27, for example. Then, the case 2 is set on aheater 28, and heated to 250 to 400° C., for example. Due to theheating, heat conducted to the case 2 made of a metal is transmitted tothe plate solder members 27, to melt the plate solder members 27. Thus,the semiconductor power devices 18 are bonded to the base portion 8 ofthe case 2. FIGS. 4B to 4E omit illustration of the plate solder members27 employed for the bonding.

Then, while the case 2 is set on the heater 28, the metal blocks 24 areset on the surfaces 181 of the semiconductor power devices 18 throughplate solder members 29, for example, as shown in FIG. 4B. Then, thecase 2 is heated to 250 to 400° C., for example. Due to the heating,heat conducted to the case 2 made of a metal is transmitted to the platesolder members 29 through the semiconductor power devices 18, to meltthe plate solder members 29. Thus, the metal blocks 24 are bonded to thesemiconductor power devices 18. FIGS. 4C to 4E omit illustration of theplate solder members 29 employed for the bonding.

Then, the top plate 3 is positioned to align the openings 14 thereofwith the metal blocks 24 respectively, and fixed to the frame portion 9,as shown in FIG. 4C.

Then, the source terminal 4 is singly placed on the heater 28, andpreliminary solder members 30 are applied onto the source terminal 4, asshown in FIG. 4D. Then, the case 2 is inverted (so that the top plate 3is directed downward) to position the metal blocks 24 on the preliminarysolder members 30, thereby bringing the metal blocks 24 into contactwith the preliminary solder members 30.

Then, the metal blocks 24 and the source terminal 4 are heated by theheater 28 to be bonded to one another, as shown in FIG. 4E.

According to the semiconductor power module 1, as hereinabove described,the metal blocks 24 larger in diameter than wires are employed as thewiring members for connecting the semiconductor power devices 18 and thesource terminal with one another. Thus, the wires (the metal blocks 24)can be bonded to the semiconductor power devices 18 with large areas.Therefore, current concentration on the junctions between the wires (themetal blocks 24) and the semiconductor power devices 18 can besuppressed. Consequently, current can be leveled. Further, the metalblocks 24 and the platelike source terminal 4 can efficiently releaseheat generated in the semiconductor power devices 18, whereby the heatreleasing effect can also be improved.

When the external terminal is the platelike source terminal 4 providedalong the upper surface of the top plate 3 as in the first embodimentand the source terminal 4 is subjected to an external shock or the like,the shock may be transmitted to the semiconductor power devices 18through the metal blocks 24, to break the semiconductor power devices 18as a result.

According to the first embodiment, therefore, the bottom wall. 26 of therecess portion 25 of the top plate 3 supports the source terminal 4 fromthe side of the rear surface thereof. Even if the source terminal 4 issubjected to a shock or the like, therefore, the bottom wall 26 of therecess portion 25 can absorb the shock. Consequently, the semiconductorpower devices 18 can be absolutely protected against transmission of theshock, or the shock transmitted to the semiconductor power devices 18can be reduced. Thus, the semiconductor power devices 18 can beprevented from breakage caused by the shock. According to the firstembodiment, further, the support portion supporting the source terminal4 is constituted of peripheral edge portions (the bottom wall 26 of therecess portion 25) of the openings 14 surrounding the metal blocks 24 inone-to-one correspondence along the plane contours of the metal blocks24, whereby the shock transmitted from the source terminal 4 to themetal blocks 24 can be effectively absorbed.

The top plate 3 is separable from the frame portion 9. In order tomanufacture the semiconductor power module 1, therefore, thesemiconductor power devices 18 are first arranged on the device region16 so that the metal blocks 24 can be bonded to the semiconductor powerdevices 18 while the top plate 3 is separated from the frame portion 9.Therefore, the semiconductor power module 1 can be manufactured withexcellent workability.

The rear surfaces 182 of the semiconductor power devices 18 are directlybonded to the base portion 8 made of a metal, whereby electrical contactwith the rear surfaces 182 (drain sides) of the semiconductor powerdevices 18 can be attained through the case 2 of the semiconductor powermodule 1.

The top plate 3 is provided with the through-hole 15, whereby aninsulated state in the case 2 can be simply maintained by pouring resininto the case 2 from the through-hole 15.

When the metal blocks 24 having a high heat releasing effect areutilized as the wire materials for the semiconductor power devices 18 asin the first embodiment, heat may be released through the metal blocks24 having a high heat releasing effect if the source terminal 4 isheated with the heater 28 while the plate solder members 27 or 29 areheld between the metal blocks 24 and the source terminal 4 as in thestep shown in FIG. 4A or 4B, for example. Consequently, the previouslyheld plate solder members 27 or 29 may not be excellently melted, butthe metal blocks 24 and the source terminal 4 may be defectively bondedto one another.

According to the first embodiment, therefore, the preliminary soldermembers 30 are previously applied to the source terminal 4 so that themetal blocks 24 are brought into contact with and bonded to the portionsprovided with the preliminary solder members 30, as shown in FIG. 4D.Thus, the metal blocks 24 and the source terminal 4 can be excellentlybonded to one another. In other words, the semiconductor power module 1can be simply manufactured in high quality.

Even if a vertical difference h is caused between the plurality of metalblocks 24 as shown in FIG. 5, for example, a prescribed volume ofpreliminary solder members 30 can compensate for the vertical differenceh according to the method. Consequently, the platelike source terminal 4can be collectively reliably bonded to the plurality of metal blocks 24.

<Second Embodiment>

FIG. 6 illustrates the overall structure of a semiconductor power moduleaccording to a second embodiment of The present invention. FIG. 7illustrates the internal structure of the semiconductor power moduleshown in FIG. 6. FIG. 8 is a sectional view of the semiconductor powermodule shown in FIG. 6, taken along a cutting plane line B-B in FIG. 6.FIG. 9 is a sectional view of the semiconductor power module shown inFIG. 6, taken along a cutting plane line C-C in FIG. 6.

A power module 51 includes a case 52 having an open surface, a top plate53 blocking the open surface of the case 52, a source terminal 54 as anexternal terminal, a source sensing terminal 55, and a gate terminal 56.

For the convenience of illustration, directions X, Y and Z shown in FIG.6 may hereinafter be employed. The direction X is a direction along thelong sides of the case 52 rectangular in plan view. The direction Y is adirection along the short sides of the case 52 rectangular in plan view.The direction Z is a direction along the height direction of the case52. When the case 52 is placed on a horizontal plane, the directions Xand Y form two horizontal directions (first and second horizontaldirections) along two horizontal straight lines (X- and Y-axes)orthogonal to each other, and the direction Z forms a vertical direction(a height direction) along a vertical straight line (a Z-axis).

The case 52 has a base portion 58, rectangular in plan view, having auniform thickness and a frame portion 59, rectangular in plan view,uprighted from a peripheral edge portion of the base portion 58. In thesemiconductor power module 51, semiconductor power devices 74, describedlater, are arranged on a region (a device region 61) of the base portion58 surrounded by the frame portion 59.

The base portion 58 is made of a metallic material in the secondembodiment. In particular, the base portion 58 is preferably made of ametal such as aluminum or copper having high heat releasingcharacteristics.

On the other hand, the frame portion 59 is made of a resin material inthe second embodiment. The frame portion 59, particularly preferablymade of heat-resistant resin such as PPS (polyphenylene sulfide), mayalternatively be made of a liquid crystal polymer or a ceramic material.

The frame portion 59 is provided with a low-stage portion 63, having aconstant depth, lower by one stage than a top portion thereof. Thelow-stage portion 63, U-shaped in plan view, is a portion for slidingthe top plate 53 also U-shaped in plan view. The depth of the low-stageportion 63 is preferably generally identical to the thickness of the topplate 53, or example. Thus, the frame portion 59 and the top plate 53can form a rectangular parallelepiped having a planar surface when thetop plate 53 is fixed.

A base 64 made of a resin material is mounted on the frame portion 59.The source sensing terminal 55 and the gate terminal 56 in the form ofnarrow columns are provided to extend inside and outside the case 52through the base 64. The source sensing terminal 55 and the gateterminal 56 are so provided through the base 64 made of resin that thesource sensing terminal 55 and the gate terminal 56 can be insulatedfrom each other and from the frame portion 59 made of a metal.

The top plate 53 is a platelike body, in the form of a rectangle havinga uniform thickness in plan view, separable from the case 52. The topplate 53 is made of a resin material in the second embodiment. The topplate 53, particularly preferably made of heat-resistant resin such asPPS (polyphenylene sulfide), may alternatively be made of a liquidcrystal polymer or a ceramic material.

The source terminal 54 is a platelike body (a plate terminal), in theform of a rectangle having a uniform thickness in plan view, elongatedalong the direction Y, and provided to be opposed to the device region61 of the base portion 58.

The top plate 53 has a pair of arm portions 65 along the long sides ofthe source terminal 54 as first opposite sides and a coupling portion 66coupling portions of the pair of arm portions 65 on a side of the sourceterminal 51 closer to the source sensing terminal 55 with each other.The top plate 53 is provided to surround three sides in the periphery ofthe source terminal 54 with the arm portions 65 and the coupling portion66, and has a blocked end blocked with the coupling portion 66 on theside closer to the source sensing terminal 55 in the direction X and anopen end opposite thereto. Thus, the top plate 53 is supported by theframe portion 59, to be slidable in a sliding direction (the directionX) along a direction where a coupling end separates from the sourceterminal 54.

As shown in FIG. 9, the pair of arm portions 54 have first portions 67coming into contact with a peripheral edge portion of the sourceterminal 54 from outside in a transverse direction (the direction Y)orthogonal to the sliding direction and second portions 68 projectingfrom lower ends of the first portions 67 along the rear surface of thesource terminal 54 respectively. Thus, the peripheral edge portion ofthe source terminal 54 along the log sides fits into a recess portion 69partitioned by the first portions 67 of the arm portions 65 and thesecond portions 68 of the arm portions 65.

As shown in FIG. 8, the coupling portion 66 has a first portion 70coming into contact with the peripheral edge portion of the sourceterminal 54 from outside in the sliding direction (the direction X) anda second portion 71 projecting from a lower end of the first portion 70along the rear surface of the source terminal 54. Thus, the peripheraledge portion of the source terminal 54 along the short sides as secondopposite sides fits into a recess portion 72 partitioned by the firstportion 70 of the coupling portion 66 and the second portion 71 of thecoupling portion 66.

In other words, the source terminal 51 is supported by the arm portions65 and the coupling portion 66 on a position U-shaped in plan view.

In the case 52, an insulated substrate 73 and the plurality ofsemiconductor power devices 74 are arranged on the device region 61surrounded by the frame portion 59 in this order from the side of thebase 64 along the direction Y.

The insulated substrate 73 is constituted of a ceramic substrate, forexample. The insulated substrate 73 is a platelike body, in the form ofa rectangle having a uniform thickness in plan view, elongated along thedirection Y, and a platelike source sensing wire 75 and a platelike gatewire 76 are formed thereon at an interval from each other. An end of thesource sensing terminal 55 is connected to the source sensing wire 75.An end of the gate terminal 56 is connected to the gate wire 76.

The plurality of semiconductor power devices 74 include a plurality ofswitching elements Tr and a plurality of diode elements Di. According tothe second embodiment, the semiconductor power devices 74 include twoswitching elements Tr and one diode element Di. The semiconductor powerdevices 74 are devices employing an SiC semiconductor in the secondembodiment. In the plurality of semiconductor power devices 74, twoswitching elements Tr are arranged at an interval from each other alongthe direction Y, and one diode element Di is arranged on a side of theswitching elements Tr opposite to the insulated substrate 73 in thedirection X. More specifically, one diode element Di and the twoswitching elements Tr are arrayed in a triangular shape in plan view.Rear surfaces 742 of the plurality of semiconductor power devices 74 arebonded to the base portion 58 of the case 52, so that the semiconductorpower devices 74 are electrically connected to the case 52.

Among the semiconductor power devices 74, the switching elements Tr areelectrically connected to the gate wire 76 and the source sensing wire75 through different Al wires 81 and 82 respectively.

Rear surfaces 832 of metal blocks 83 employed as wiring materialssupplying power to the semiconductor power devices 74 are bonded one byone to surfaces 741 (opposite to the rear surfaces 742 bonded to thebase portion 58) of the semiconductor power devices 74. The metal blocks83 are in the form of rectangular parallelepipeds uprighted from thesurfaces 741 of the semiconductor power devices 74 in a direction(approaching the source terminal 54) separating from the base portion 58in the second embodiment.

The metal blocks 83 are preferably made of Cu or an alloy material (suchas a CuMo alloy or a CuW alloy, for example) containing Cu. Thus, thedifference between the linear expansion coefficients of SiC and themetal blocks 83 can be reduced as compared with a case of employing Alwires as wiring members for the SiC power devices 71. Therefore, thermalstress caused between the semiconductor power devices 74 and the metalblocks 83 can be reduced. Consequently, thermal fatigue of thesemiconductor power devices 74 can be reduced, whereby a semiconductorpower module 51 having a long life and high reliability can be attained.For example, the linear expansion coefficient of SiC is about 4.5 ppm/K,and that of a CuMo alloy is about 9.0 ppm/K (about twice the linearexpansion coefficient of SiC). On the other hand, the linear expansioncoefficient of Al is about 23 ppm/K (about five times the linearexpansion coefficient of SiC). Surfaces 831 of the plurality of metalblocks 83 are bonded to the source terminal 54 in a region of the topplate 53 surrounded by the arm portions 65 and the coupling portion 66.

FIGS. 10A to 10E are sectional views successively illustratingmanufacturing steps for the semiconductor power module 51 show in FIG.6.

First, the insulated substrate 73 provided with the platelike wires 75and 76 is mounted on the device region 61 in the case 52, as shown inFIG. 10A Then, the base 64 having the source sensing terminal 55 and thegate terminal 56 inserted thereinto is mounted on the frame portion 59of the case 52. Then, the source sensing terminal 55 and the gateterminal 56 and the platelike wires 75 and 76 are bonded to one another.Then, the semiconductor power devices 74 are set on the base portion 58through plate solder members 84, for example. Then, the case 52 is seton a heater 85, and heated to 250 to 400° C., for example. Due to theheating, heat conducted to the base portion 58 made of a metal istransmitted to the plate solder members 84, so melt the plate soldermembers 84. Thus, the semiconductor power devices 74 are bonded to thebase portion 58 of the case 52. FIGS. 10B to 10E omit illustration ofthe plate solder members 84 employed for the bonding.

Then, while the case 52 is set on the heater 85, the metal blocks 83 areset on the surfaces 741 of the semiconductor power devices 74 throughplate solder members 36, for example, as shown in FIG. 10B. Then, thecase 52 is heated to 250 to 400° C., for example. Due to the heating,heat conducted to the base portion 58 made of a metal is transmitted tothe plate solder members 86 through the semiconductor power devices 74,to melt the plate solder members 86. Thus, the metal blocks 83 arebonded to the semiconductor power devices 74, FIGS. 10C to 10E omitillustration of the plate solder members 86 employed for the bonding.

Then, the source terminal 54 is singly placed on the heater 85, andpreliminary solder members 87 are applied onto the source terminal 54,as shown in FIG. 10C, Then, the case 52 is inverted to position themetal blocks 83 on the preliminary solder members 67, thereby bringingthe metal blocks 83 and the preliminary solder members 87 into contactwith one another.

Then, the metal blocks 83 and the source terminal 54 are heated by theheater 85 to be bonded to one another, as shown in FIG. 10D.

Then, the sop plate 53 is positioned to align the recess portion 72thereof with the peripheral edge portion of the source terminal 54, andthe top plate 53 is slid with respect to the frame portion 59 until shecoupling portion 66 thereof comes into contact with the source terminal54, as shown in FIG. 10E. Thus, the device region 61 is blocked.

According so the semiconductor power module 51, as hereinabovedescribed, the metal blocks 83 larger in diameter than wires areemployed as the wiring members for connecting the semiconductor powerdevices 74 and the source terminal 54 with one another. Thus, the wires(the metal blocks 83) can be bonded to the semiconductor power devices74 with large areas. Therefore, current concentration on the junctionsbetween the wires (the metal blocks 83) and the semiconductor powerdevices 74 can be suppressed. Consequently, current can be leveled.Further, the metal blocks 83 and the platelike source terminal 54 canefficiently release heat generated in the semiconductor power devices74, whereby a heat releasing effect can also be improved.

When the external terminal is the platelike source terminal 54 providedalong the upper surface of the top plate 53 as in the second embodimentand the source terminal 54 is subjected to an external shock or thelike, the shock may be transmitted to the semiconductor power devices 74through the metal blocks 83, to break the semiconductor power devices 74as a result.

According to the second embodiment, therefore, the second portions 68and 71 of the arm portions 65 and the coupling portion 66 of the topplate 53 support the source terminal 54 from the side of the rearsurface thereof. Even if the source terminal 54 is subjected to a shockor the like, therefore, the arm portions 65 and the coupling portion 66can absorb the shock. Consequently, the semiconductor power devices 74can be absolutely protected against transmission of the shock, or theshock transmitted to the semiconductor power devices 74 can be reduced.Thus, the semiconductor power devices 74 can be prevented from breakagecaused by the shock.

The top plate 53 is slidably supported by the frame portion 59, andseparable from the frame portion 59. In order to manufacture thesemiconductor power module 51, therefore, the semiconductor powerdevices 74 are first arranged. on the device region 61 so that the metalblocks 83 can be bonded to the semiconductor power devices 74 while thetop plate 53 is separated from the frame portion 59. Therefore, thesemiconductor power module 51 can be manufactured with excellentworkability. Further, an end portion of the top plate 53 opposite to thedirection where the same is extracted by sliding is open. Also after thetop plate 53 is fixed to the frame portion 59, therefore, the deviceregion 61 can be exposed by extracting the top plate 53 withoutdetaching the metal blocks 83 from the source terminal 54. Consequently,maintenance in the case 52 can be easily performed.

The peripheral edge portion along the long sides of the source terminal54 fits into the recess portion 69 partitioned by the first potions 67of the arm portions 65 and the second portions 68 of the arm portions65. When the top plate 53 is slid along the frame portion 59, therefore,the source terminal 54 can be utilized as a guide member for guiding thetop plate 53. Therefore, the top plate 53 can be easily positioned.

The peripheral edge portion along the short sides (opposite sidesorthogonal to the sliding direction) of the source terminal 54 fits intothe recess portion 72 partitioned by the first portion 70 of thecoupling portion 66 and the second portion 71 of the coupling portion66. When the top plate 53 is slid along the frame portion 59, therefore,the sliding of the top plate 53 can be stopped by bringing theperipheral edge portion of the source terminal 54 into contact with thefirst portion 70 of the coupling portion 66 of the top plate 53. inother words, the source terminal 54 can also be utilized as a stoppermember for stopping the sliding of the top plate 53. Therefore, the topplate 53 can be more easily positioned.

The rear surfaces 742 of the semiconductor power devices 74 are directlybonded to the base portion 58 made of a metal, whereby electricalcontact with the rear surfaces 742 (drain sides) of the semiconductorpower devices 74 can be attained through the case 52 of thesemiconductor power module 51.

When the metal blocks 83 having a high heat releasing effect areutilized, as the wire materials for the semiconductor power devices 74as in the second embodiment, heat may be released through the metalblocks 83 having a high heat releasing effect if the source terminal 54is heated with the heater 85 while the plate solder members 84 or 86 areheld between the metal blocks 83 and the source terminal 54 as in thestep shown in FIG. 10A or 10B, for example. Consequently, the previouslyheld plate solder members 84 or 86 may not be excellently melted, butthe metal blocks 83 and the source terminal 54 may be defectively bondedto one another.

According to the second embodiment, therefore, the preliminary soldermembers 87 are previously applied to the source terminal 54 so that themetal blocks 83 are brought into contact with and bonded so the portionsprovided with the preliminary solder members 87, as shown in FIG. 10C.Thus, the metal blocks 83 and the source terminal 54 can be excellentlybonded to one another. In other words, the semiconductor power module 51can be simply manufactured in high quality.

Even if the vertical difference h shown in FIG. 5 is caused between theplurality of metal blocks 83 as described in the aforementioned firstembodiment, for example, a prescribed volume of preliminary soldermembers 87 can compensate for the vertical difference h according to themethod. Consequently, the platelike source terminal 54 can becollectively reliably bonded to the plurality of metal blocks 83.

While the embodiments of the present invention have been described, thepresent invention may be embodied in other ways.

For example, the metal blocks 24 may alternatively have tapered shapeswhose sectional areas spread from the rear surfaces 242 toward thesurfaces 241 thereof, as in a power module 101 shown in FIGS. 11 and 12.

Further, the material for the metal blocks 24 or 83 may alternatively beprepared from a metallic material such as Cu, Al or Fe.

While the present invention has been described in detail by way of theembodiments thereof, it should be understood that these embodiments aremerely illustrative of the technical principles of the present inventionbut not limitative of the invention. The spirit and scope of the presentinvention are to be limited only by the appended claims.

This application corresponds to Japanese Patent Application No.2010-219030 filed with the Japan Patent Office on Sep. 29, 2010, thedisclosure of which is incorporated herein by reference.

What is claimed is:
 1. A semiconductor device comprising: a base member;an SiC semiconductor having a bonding surface and a rear surface withthe rear surface bonded to the base member; a metal block, having abonding surface and a rear surface with the rear surface of the metalblock being bonded to the bonding surface of the SiC semiconductor,uprighted from the bonding surface of the SiC semiconductor in adirection separating from the base member and employed as a wiringmember for the SiC semiconductor; an external terminal bonded to thebonding surface of the metal block and employed as a terminal for theSiC semiconductor; an insulated substrate; and a wiring, formed on anupper surface of the insulated substrate, being connected to the bondingsurface of the SiC semiconductor.
 2. The semiconductor device accordingto claim 1, wherein the SiC semiconductor includes a plurality of SiCsemiconductors, and the bonding surface of the SiC semiconductors is aplurality of bonding surfaces, wherein the external terminal is commonlyconnected to the bonding surfaces of the plurality of SiCsemiconductors.
 3. The semiconductor device according to claim 1,wherein the metal block is made of Cu or an alloy material containingCu.
 4. The semiconductor device according to claim 1, further comprisinga second semiconductor power device being a different device type fromthat of the SiC semiconductor.
 5. The semiconductor device according toclaim 1, wherein the metal block is in the form of a rectangularparallelepiped.
 6. The semiconductor device according to claim 1,wherein the metal block has a tapered shape whose sectional area spreadsfrom the rear surface of the metal block toward the bonding surface ofthe metal block.
 7. The semiconductor device according to claim 2,wherein the metal block includes a plurality of metal blocks bonded toeach of the SiC semiconductors, and the rear surface of the metal blocksincludes a plurality of rear surfaces, the rear surfaces of the metalblocks being bonded to the bonding surfaces of the plurality of the SiCsemiconductors, respectively, wherein the external terminal iscollectively bonded to the metal blocks.
 8. The semiconductor deviceaccording to claim 1, further comprising: a case having a base portionprovided with a device region where the SiC semiconductor is arranged,and a frame portion fixed to the base portion for surrounding the deviceregion; and a top plate, made of resin, fixed to the frame portion ofthe case and opposed to the device region, wherein the external terminalincludes a plate terminal provided along the top plate, the top platehas a support portion overlapping with the plate terminal in a plan viewfor supporting the plate terminal from a side of a rear surface of theplate terminal, the top plate is provided with a through-hole passingthrough the top plate in a thickness direction of the top plate in aregion other than a region overlapping with the plate terminal in theplan view.
 9. The semiconductor device according to claim 1, furthercomprising a second semiconductor power device having a thicknessdifferent from that of the SiC semiconductor.
 10. A semiconductor devicecomprising: a base member; a semiconductor power device having a bondingsurface and a rear surface with the rear surface bonded to the basemember; a metal column, having a bonding surface and a rear surface withthe rear surface of the metal column being bonded to the bonding surfaceof the semiconductor power device, uprighted from the bonding surface ofthe semiconductor power device in a direction separating from the basemember and employed as a wiring member for the semiconductor powerdevice; an external terminal bonded to the bonding surface of the metalcolumn and employed as a terminal for the semiconductor power device; aninsulated substrate; and a wiring, formed on an upper surface of theinsulated substrate, being connected to the bonding surface of thesemiconductor power device.
 11. The semiconductor device according toclaim 10, wherein the semiconductor power device is employing an SiCsemiconductor.
 12. The semiconductor device according to claim 10,wherein the metal column is comprised of a metal block.
 13. Asemiconductor device comprising: a base member; a semiconductor powerdevice having a bonding surface and a rear surface with the rear surfacebonded to the base member; a metal block, having a bonding surface and arear surface with the rear surface of the metal block being bonded tothe bonding surface of the semiconductor power device, uprighted fromthe bonding surface of the semiconductor power device in a directionseparating from the base member and employed as a wiring member for thesemiconductor power device; an external terminal bonded to the bondingsurface of the metal block and employed as a terminal for thesemiconductor power device; a case having a base portion provided with adevice region where the semiconductor power device is arranged, and aframe portion fixed to the base portion for surrounding the deviceregion; and a top plate, made of resin, fixed to the frame portion ofthe case and opposed to the device region, wherein the external terminalincludes a plate terminal provided along the top plate, the top platehas a support portion overlapping with the plate terminal in a plan viewfor supporting the plate terminal from a side of a rear surface of theplate terminal, and the top plate is provided with a through-holepassing through the top plate in a thickness direction of the top platein a region other than a region overlapping with the plate terminal inthe plan view.
 14. The semiconductor device according to claim 13,wherein the semiconductor power device is employing an SiCsemiconductor.